The present invention relates to an improved laser beam pulse generating apparatus and more particularly for use with a metal-vapor laser such as a copper vapor laser.
The copper vapor laser CVL is one of a number of electric-discharge-excited metal-vapor lasers that are characterized by laser transitions from an excited state to a low-lying metastable state. Laser oscillator power in CVLs has been increased from the milliwatt level to hundreds of watts at operating ranges of 5-20 kilohertz (or more).
The increase in power levels has resulted, in part, by increasing the diameter of the CVL discharge tube. However, with the increase in the diameter of a CVL discharge tube, problems have been encountered which affect the output power levels.
One effect is known as radial dynamics, which limits the uniform buildup of a laser pulse from the outside of the discharge tube to the center. See, for example, the article by M. J. Kushner and B. E. Warner entitled "Large-Bore Copper-Vapor Lasers: Kinetics and Scaling Issues," J. Appl. Phys. 54 (6) 1983, p.2970. Because of the radial dynamics effect, the leading edge of the laser pulse increases in intensity with time from the outside of the discharge tube to its center. This results in the generation of a nonuniform pulse having what can be characterized as a chevron shaped intensity pattern with respect to time. This can seriously affect the proper operation of any system utilizing a CVL having high power, high repetition rate laser pulse outputs which are supposed to be uniform in intensity. Moreover, with high power, high repetition rate CVL systems, heat buildup within the tubular structure can still further limit the usable discharge tube diameter by thermally populating the metastable lower laser level. The heat buildup problem can further limit the desired increased higher power level of such a CVL system.